In the design of modern vehicles, implementing security technology and multimedia applications, design engineers are anew confronted with problems which were originally known only in computer technology. The data rates of the cables are rising rapidly, whereby requirements regarding the electrical cables and connection systems in vehicles increase. With today's transmission rates of 100 Mbit/s and in future far more, high frequency influences play an ever increasing role. Today, the entire transmission path needs to be considered in the design of the line set, since it is not only a sequence of connectors and cables. Transmission systems, such as e.g. Broad-R Reach, have specific requirements for the associated transmission channel. Among other things, these are the maximum allowed reflections within the bandwidth relevant to the system. The reflection performance of the transmission path is characterized by the reflection attenuation in the relevant frequency range. In an analog way, characterization in the time domain is possible by the variation of the impedance along the transmission path, since changes of the wave length on the path are the cause of reflections. The variation of the impedance is measured using a time domain reflectometer (TDR). In this case, the reflected signal, when excited by a step function, is recorded and the time variation Z(t) of the impedance is determined therefrom.
Only the frequency components of the reflected signal within the system-relevant bandwidth are of importance for the quality of the transmission path. With TDR the result Z(t) is filtered accordingly or the stimulating step function is limited in its rise time. With Broad R Reach standard, the specified rise time is tr=700 picoseconds. For the local variation the bandwidth limit acts as reduced spatial resolution. The result in the end is a system-relevant variation of impedance.
With respect to the optimum impedance, standard connector systems have generally a system-relevant value which is too high due to component geometry and material properties which are not to be changed. In particular, the areas in which the carrier medium of the signals changes, for example, from circuit board to connector or from connector to electrical line, cause major problems. In today's technology, mainly lines for transmission of data are used having two mutually twisted wires (twisted pair). These lines have good transmission characteristics, as long as the wires of the line are close to each other. If the wires are separated from each other, which inevitably is the case when connecting the wires with a connector, the transmission characteristics of the line change significantly. The conductive elements in the connector, which is connected to the line, normally do not correspond in geometry to the route of the wires. The design of the connector is within constructive limits, which are largely dictated by space and costs. Available connector systems that accommodate the requirements of high data rates are usually expensive and inflexible. Therefore, difficulties in adjustment between connector and cable cannot be completely avoided.